The present disclosure relates to a roller drive transmission device for transmitting a drive force to a roller and an automatic document feeder and an image forming apparatus provided with the same.
Conventionally, a sheet feeder is known as an apparatus provided with a roller drive transmission device. This sheet feeder includes a pickup roller for feeding a sheet, a sheet feed roller for conveying the sheet on a side downstream of the pickup roller and a separation pad for separating sheets one by one by being held in contact with the sheet feed roller.
The sheet feed roller is rotationally driven by a drive force transmission device. The drive force transmission device is provided with a power input unit including a projection, a power transmission unit including an engaging groove and a locking claw, and a power output unit including a ratchet groove and configured to integrally rotate with the sheet feed roller. According to an axial movement of the power transmission unit, the transmission of a drive force from the power input unit to the power output unit is switched.